African-Americans have lower levels of a key protein associated with Alzheimer's disease, which could keep blacks with the disease from being diagnosed, according to Washington University researchers.

In a 12-year study of 1,255 participants, the researchers found black patients have a much lower baseline level of the protein tau, which is present in higher amounts in patients with the neurodegenerative disease. Because doctors look for the protein when diagnosing Alzheimer's, lower levels in black patients mean they may not be diagnosed as quickly as their white counterparts.

As a result, black patients — already disproportionately affected by the disease — may not receive proper care, the study's authors said.

The different protein levels indicate “the disease may develop differently in African-Americans compared to whites,” Morris said. “We’re developing therapies based on what we think the disease mechanisms are. And if they differ in racial groups, we need to know that, because we may need to develop different therapies.”

In healthy brains, the protein helps hold up brain cells. In Alzheimer’s patients, the proteins detach and stick to each other, which blocks communication between neurons. Research suggests it builds up in brain regions that control memory.

Doctors and researchers call such proteins “biomarkers,” because higher levels are found in patients with Alzheimer’s.

Disease patterns in both white and black patients indicate that rising tau levels are associated with cognitive impairment. But African-Americans had much more lower levels of the protein to start out with. Even when they rose in black patients, it wasn’t to the level that was seen in white patients.

That’s important because researchers are increasingly finding that biomarkers such as the tau protein are important predictors of the disease. The effects Alzheimer’s has on the brain are sometimes in place decades before symptoms, such as memory loss, appear.

Many recent clinical trials attempting to treat symptomatic Alzheimer’s patients have failed. Those failures indicate the best treatment for the disease will have to be administered after brain chemistry starts changing, but before patients start showing cognitive decline, said Morris, the director of the university’s Knight Alzheimer’s Disease Research Center.

To create and study those therapies, researchers need to take how the disease affects people of different races into account, he said. For the study, he and his colleagues close to 200 African-American patients, who made up 14 percent of the total participants.

But getting to that point hasn’t been easy, he said. Researchers have found it difficult to include African-Americans in their studies — in part because many black people don’t trust a medical system that has long ignored or abused them, he said.

For example, between the 1930s and the 1970s, the U.S. Health Service infected black men with syphilis without their knowledge to study the disease. The Tuskegee Experiment still looms in the minds of many African-Americans.

And hospitals and research institutions have a long history of shutting black patients out.

“In the 1960s and '70s there still was racial discrimination at Barnes hospital” Morris said. “Patients had to be seen in the basement.”

Now, people of that generation are old enough to be enrolled in research studies, Morris said.

“They see Wash U and Barnes Hospital as discriminatory, even though we’re trying to erase that,” he said.